LIMESTONE COUNTY, Ala. (WHNT) — A man authorities believed to be connected to the murders of five people in the Birmingham area over a decade ago has died in prison.

Martez Seay, 39, was found unresponsive in his cell at the Limestone Correctional Facility on Monday, August 7, according to the Alabama Department of Corrections (ADOC). He was taken to the health care unit where he was pronounced dead.

According to AL.com, Seay pleaded guilty to capital murder in 2011 following a seven-month crime spree. Within that plea, the article states that Seay admitted to:

• The November 2008 shooting death of Christian Callins, 24, during a robbery attempt, and the shooting death of an accomplice in Callins’ murder, Gregory Shelton Jr., 27.
• The December 2008 shooting deaths of Osmond Williams, 20, and Darrelle Sampson, 17.
• The May 2009 shooting death of Lonnie Vaughn, 44, while robbing him of cash and a sports utility vehicle.
• The June 2009 conspiracy to kill Kandi Hawkins to keep her from testifying against him in the Vaughn case

Seay additionally pleaded guilty to conspiracy to commit murder in the 2008 shooting of his girlfriend, Hawkins, who was left paralyzed. His mother, Yolanda Seay, was also convicted of conspiracy to commit murder in Hawkins’ shooting.

The AL.com article also recalled that Seay had been featured in an episode of “The First 48,” adding that investigators named Seay as the triggerman in “at least four of the six shootings and a main player in all six.”

The ADOC Law Enforcement Services Division is looking into Seay’s death, with any official cause of death pending an autopsy.